Magnetic resonance tomography is a well-known and long-established imaging technology which is mainly employed in the medical imaging field. In most cases recording magnetic resonance image data takes a relatively long time, since for example a plurality of layers must be recorded one after another, and the like. Moreover, movements during the recording of an image lead to undesirable artifacts which have a detrimental effect on the image quality. Apart from other movements this applies in particular in the case of respiratory movements. For this reason magnetic resonance devices are known which at certain time instants during the recording of the image data output what are known as breath-hold commands so that a patient who is the subject of a magnetic resonance image data acquisition can hold his or her breath for a certain period of time and as a result motion artifacts can be avoided. In the magnetic resonance tomography of ventilated patients there is however the problem that said conventional breath-hold commands, which are issued automatically by the magnetic resonance device, do not work correctly. It has therefore been proposed that a ventilation apparatus will be briefly stopped manually during the recording of magnetic resonance image data whenever the operator of the magnetic resonance device issues a corresponding command to an anesthetist actuating the ventilation apparatus. This process is complicated and prone to error and optimal results cannot be obtained.
With regard to other imaging techniques, solutions have already been discussed which are aimed at improving the image quality in the event of a respiratory movement or indeed to avoid respiratory movement artifacts. Thus, it is provided in DE 10 2008 032 827 A1 to take into account in the reconstruction of the image data a ventilation signal of a ventilation device used in any case for ventilating a patient under general anesthetic who is being examined by means of a medical imaging system, so that no separate device for measuring the respiratory movement is required. For example, the ventilation signal can be used for gating in respect of the respiration. In DE 10 2008 030 891 A1 it is proposed to interrupt the ventilation of an anesthetized patient by means of a ventilation device as a function of a sensed operating status of a medical system fully automatically for the duration of a diagnostic or therapeutic examination. The intention in doing this is to relieve the pressure on the medical personnel.
A common feature of the two cited possibilities is that they are very poorly suited to use in connection with magnetic resonance tomography, which is due in particular to the duration of the recording of the magnetic resonance image data. Thus, there is no question of the ventilation device (ventilation apparatus) being stopped for the entire duration of the image recording session. The condition of many patients who are to undergo examination is poor, so that only very brief ventilation pauses, if any, are conceivable. The long duration of the pulse sequences in magnetic resonance also conflicts with the idea of controlling the start of the magnetic resonance acquisition as a function of the ventilation cycle, because a certain time elapses until magnetic resonance image data is actually measured and the respiratory position changes. Consequently, techniques such as those cited above, which are designed for x-ray-based imaging methods, are only usable to a very limited extent within the framework of magnetic resonance.